17 Jan
2023
17 Jan
'23
5:14 p.m.
On Jan 17, 2023, at 5:09 PM, Chuck Guzis via cctalk
<cctalk(a)classiccmp.org> wrote:
On 1/17/23 13:58, Paul Koning via cctalk wrote:
Yes indeed. Triggering the emergency retract with the drive open for service could easily
take off fingers. The amount of power involved in moving those head stacks around is
pretty substantial.
paul
No, 844 drives use linear voice coils (linear motors), which seems to have become the
norm in the early 1970s. RK05 is another example. The term "voice coil" is
used because they look like oversized versions of the coil that drives the speaker cone in
loudspeakers. These all are some sort of servo device; in many of them the servo signal
is on the media, but not always. For example, the RK05 uses a pattern of lines on a glass
substrate attached to the actuator; the "fault" light on the drive indicates a
failure of the light bulb that illuminates the servo pattern.
A common feature of linear motor actuators is an emergency retract circuit, powered by
rather large capacitors, to pull the heads off the disk if there is a power failure.
And, IIRC, a bit red warning sticker on the actuator.
--Chuck